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Adaptations to stag beetle weaponry and its ecological consequences

Adaptations to stag beetle weaponry and its ecological consequences. Jana Goyens , Joris Dirckx, Peter Aerts. Laboratory for Functional Morphology University of Antwerp , Belgium Laboratory of BioMedical Physics . Introduction : stag beetle armature. Stag beetle family:

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Adaptations to stag beetle weaponry and its ecological consequences

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  1. Adaptations to stag beetle weaponryand its ecological consequences Jana Goyens, Joris Dirckx, Peter Aerts LaboratoryforFunctionalMorphologyUniversity of Antwerp, Belgium Laboratoryof BioMedical Physics

  2. Introduction: stag beetlearmature Stag beetle family: • Large male mandibles (jaws) • High diversity in size and shape: Cyclommatusmetallifer Prosopocoilusumhangi Aegognathuswaterhousei Allotopusmoellenkampi

  3. Introduction: stag beetlearmature Mandiblesused as armature in fights Malesfighteachother over matingopportunities: Youtube, Tammy Bergström

  4. Introduction: stag beetlearmature Aims: • Adaptations of headmorphologyto make mandiblesuseful tools? mandiblebite force • Morphologicaladaptationsto move aroundwith heavy and large armature?stabilityand efficiency

  5. Mandiblebite force Malesbite more forcefully: ♂: 6.9 ± 2.0 N normalized: 849.2 ♀: 1.1 ± 0.4 N normalized: 285.2 ♀

  6. Mandiblebite force Higher male bite force DESPITE mechanical disadvantage (output lever) Explanations: • Longer input lever: compensationfor long output lever • Largerbitemuscles(microCT-scans) • Malesandfemalesalmostoptimalmuscle fiber direction(CT-scans) Conclusion: Male headsizeandshapedrasticallychanged toproduce high biteforces ♀ ♂

  7. Locomotion • Alternatingtripodgait • Staticstabilitypossible • Stabilitymargin: • Perpendiculardistancetoedge support triangle • Negativewhenoutsidetriangle Heavy male head CAUSES impaired running: • (static) instability:

  8. Locomotion Heavy male head CAUSES impaired running: • (static) instability:

  9. Locomotion Heavy male head CAUSES impaired running: • (static) instability: • Verycostinefficient Cost of transport: ♂: 4.15 ± 1.13 Jm-1kg-1 ♀: 2.52 ±0.76 Jm-1kg-1 Males 40% highercost of transport

  10. Conclusions Male stag beetles are completelyadaptedto male-male fights: • Diversificationandenlargement of mandiblestroughoutLucanidae family • Head sizeandshapeadaptedfor high biteforces • Large ecologicalconsequences • Staticinstability: malesoccasionallybounceagainst the groundwiththeirhead • High locomotion cost

  11. Thankyouforyour attention! • Acknowledgements: • Ministry of Youth and Sport of Azerbaijan Republic • Azerbaijan Young Scientists, Postgraduate and Masters Union (AYSPMU) • Eurodoc • University of AntwerpDehoussegrant

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